Molding of all-plastic shot shell cases

ABSTRACT

The molding of all-plastic shot shell cases wherein the case has a base wall with substantially smooth inside and outside surfaces and the case sidewall which has a smooth interior surface and a smooth or striated or slightly corrugated outer surface is integral therewith; gating the plastic into the mold at the center of the base wall and causing the plastic to flow first to all portions of the periphery of the base wall and then progressively along all portions of the longitudinal case sidewall, the mold ejecting the case by a sleeve bearing against the open end of the case sidewall to loosen the case from the mold core and an ejector pin within the core completing ejection of the case from the cavity.

United States Patent [72] Inventor Duane S. Stenmo Rush City, Minn. [21]Appl. No. 859,943 [22] Filed Sept. 22, 1969 [4S] Patented July 13, 1971[73] Assignee Herter's, Inc.

Waseca, Minn.

[54] MOLDING 0F ALL-PLASTIC SHOT SHELL CASES 2 Claims, 2 Drawing Figs.

[52] 1.1.8. Cl. 18/42 D [51] int. Cl B29c 1/14 [50] Field ofSearch 18/30RM, 30 WJ, 30 WC, 30 WM, 30 WN, 42 D [56] References Cited UNITED STATESPATENTS 2,339,443 1/1944 Wilson .1 18/42 D 2,524,858 10/1950 Thomas2,929,105 3/1960 Starcketal ABSTRACT: The molding of all-plastic shotshell cases wherein the case has a base wall with substantially smoothinside and outside surfaces and the case sidewall which has a smoothinterior surface and a smooth or striated or slightly corrugated outersurface is integral therewith; gating the plastic into the mold at thecenter of the base wall and causing the plastic to flow first to allportions of the periphery of the base wall and then progressively alongall portions of the longitudinal case sidewall, the mold ejecting thecase by a sleeve bearing against the open end of the case sidewall toloosen the case from the mold core and an ejector pin within the corecompleting ejection of the case from the cavity.

PATENTEU JUL 1 3 1971 DIM/VF 5, S TEA/M0 WM i 7W MOLDING OF ALL-PLASTICSHOT SHELL CASES BRIEF SUMMARY OF THE INVENTION The mold assembly forthe all-plastic shot shell case gates the plastic into the mold cavityat a location centrally of the base wall of the case being molded andthe plastic flows radially in all directions to first form the base wallof the case and then simultaneously to all peripheral portions of thecase sidewall, progressively from the end immediately adjacent the basewall to the open mouth end of the case. The ejection of the case fromthe mold assembly when opened is effected by a sleeve bearing againstthe end edge of the case wall so as to push the case off the mold core.The ejection is then completed by an ejector pin sliding through thecore after the end of the pin has formed the inside surface ofthe base.wall of the case during the molding.

The all-plastic shot shell case can be molded ofa number of plastics ora mixture of plastics, such that the case has sufficient tensile, shearand impact strength as to withstand the pressures encountered uponfiring a shot shell in the chamber of a shotgun. The plastic may bepolycarbonate, or may be a mixture of polycarbonate and other plastics,such as polyethylene; the polycarbonate is commercially available fromseveral places, such as Lexan from General Electric Company,Schenectady, New York, and other equivalent materials.

In the drawing,

FIG. 1 is a section view of the principal elements of the mold assemblyshown in closed condition during the formation of an all-plastic shotshell case.

FIG. 2 is a detail section view of the movable mold assembly shown inshifted position during which ejection of the molded shot shell case isbeing effected.

DETAILED DESCRIPTION OF THE INVENTION The all-plastic shot shell casemade according to the present invention is illustrated in FIG. 2 and isindicated by the numeral 10. In FIG. 2 the molded case is being ejectedfrom the mold assembly and is complete and ready for further processingin the formation of a shot shell. The case has a base wall 11 and acentral sprue 12. The outer surface 13 of the base wall may have lettersor numerals formed as depressions therein, or it may be that the outersurface 13 will be smooth without such lettering or numbers. The innersurface I4 of the base wall 11 is essentially smooth.

The case sidewall 15 has a smooth inner surface and a smooth or striatedor slightly corrugated outer surface, and, although it is substantiallyof uniform thickness throughout the length, it may taper to a slightlythinner dimension at the extreme outer end, opposite the base wall 11.The end edge 16 of the case sidewall is smooth and free of anyirregularities and is therefore well adapted for crimping to form theclosure for the shot shell when the shot shell is loaded with powder andshot, and wadding.

With respect to the formation of a shot shell from the case 10, itshould be understood that the central portion of the base wall 11 willbe bored out to remove the sprue 12 and to form a primer hole forreceiving the primer which will be gripped and held in the properlocation by a soft plastic base wad which will be formed of polyethyleneor other soft and resilient plastic material.

The case will thereupon receive its usual charge of powder, wadding,preferrably a shot cup, and then the shot charge and closure. Theclosure may be effected by the use of a closure wad or by the use ofastar crimp.

Because the primer hole at the central portion of the base wall II isbored out, the gating of the plastic into the mold for forming the case10 can be effected at the center of the base wall without forming anyimperfections in the molded part which are frequently associated withthe gating of any plastic part being molded. It is very desirable thatthe gating of a plastic be effected at the center of the base wall sothat the plastic, as it is filling the cavity, will fill all peripheralportions simultaneously, progressively radially outwardly across thebase wall 111 in all directions and then longitudinally along thesidewall 15 so that the entire case 10 is formed without any weld seamsin the plastic due to flow of plastic in filling the mold cavity.

The mold assembly illustrated in FIGS. 1 and 2 includes a stationarymold assembly, indicated in general by numeral 17, and a movable moldassembly 18 which is mounted on the ram of the mold press and moves withthe ram. The stationary mold assembly 17 includes a mounting plate 19which carries the insert part 20 which receives the nozzle 21. Theinsert is held in the mounting plate 19 by the clamp plate 22 which alsomounts the plastic manifold 23 through which the plastic material isdelivered to the nozzle 21, and, as seen, the nozzle 21 may be connectedto the manifold in any suitable way, such as the threads as illustrated.Of course, suitable cooling is applied to all of the parts associatedwith the stationary mold assembly 17 so as to maintain the plastic atpredetermined temperatures for proper gating.

The insert part 20 defines the mold surface 20a for forming the outsideof the base wall 11 of the shot shell. The insert part 20 also definesmating surfaces for mating with the cavity part 24 of the movable moldassembly 18.

The movable mold assembly 18 also includes a mounting plate 25 whichmounts the cavity part 24, and a clamp plate 26 secured to the mountingplate 25 for retaining the cavity part 24 in the desired position. Themovable'mold assembly 18 also includes the hollow core 27 extendingthrough the cavity part 24 to the end face thereof for forming theinside surfaces of the shot shell case 10 being molded. The hollow core27 is mounted in a plate 28 and secured therein by a clamp plate 29affixed to the mounting plate 28. The cavity part 28 is slidable alongthe core 27 for producing the initial ejection movement of the moldedpart or case 10 when the mold is opened, and, as illustrated in FIG. 2,the mounting plate 25 together with the clamp plate 26 is urged alongthe core 27 by a spring construction 30 or an equivalent springconstruction elsewhere on the mold assembly. A stripper sleeve 31 ismounted in the cavity part 24 and is held therein by the clamp plate 26.The sleeve 31 has a shoulder surface 32 which defines the end of thecavity between the core 27 and the cavity part 24, thereby forming theend edge 16 of the shot shell case 10. The sleeve 31 also bears againstthis end edge 16 of the case after the part is formed and as the mold isbeing opened so that the sleeve 31 produces the initial endwise movementof the case 10 along the core 27.

In FIG. 2, the initial movement of the case along the core 27 hasalready been completed, and the additional ejecting movement of the case10 is being produced by the central core pin 33 which extends throughthe hollow core 27 with the end of the core pin 33 defining the insidesurface or face 14 of the base wall 11 of the shot shell case.

In FIG. 2, the ejector pin 33 is shown advanced well beyond the end ofthe core 27 so as to produce the final ejection of the case, looseningand moving the case 10 out of the cavity part 24. The ejector pin 33 isoperated by a motion separate from the motion of the ram of the press inwhich the mold assembly is mounted.

It will be seen that I have provided for molding of a plastic shot shellcase by gating the plastic into the cavity from the central area of thebase wall of the shot shell case being formed which base wall is boredout in order to define a primer hole before the actual shot shell iscompleted for firing. The mold assembly separates and the initialmovement of the completed shot shell case off the core is produced bythe stripper sleeve which bears against and moves the end edge surfaceof the peripheral sidewall of the case, thereby preventing the formationof any part-weakening ejection marks. The case being formed in thecavity is produced without any weld lines whatever because of thesimultaneous filling around the entire periphery of the cavity and thenprogressively outwardly across the base wall and then progressivelyalong the sidewall as the cavity is being filled.

ble mold assembly including a core forming the inside of the shot shellcase, a cavity mold part encompassing the core and defining the cavityin which the case is formed, the cavity part cooperating with the insertpart of the sta tionary assembly to close the mold, said cavity partineluding a stripper sleeve encompassing the core in close relation todefine the end of the cavity and to form the end edge of the shot shellcase sidewall, the cavity part being movable along the core when themold is open to initiate ejection of the shot shellcase from the core asthe stripper sleeve slides along the core, the core having alongitudinal central opening through which an ejector pin extends andslides, to remove the case from the cavity part by pushing against theinside of the base wall of the case being formed. 2. The inventionaccording to claim 1 and said core and said stripper sleeve havingmating tapers engaging each other and retaining the core concentric ofthe cavity.

1. A mold assembly for producing all-plastic shot shell cases, astationary mold assembly including an insert part forming the base wallof the shot shell case and having a nozzle gating plastic centrally ofthe base wall of the shot shell case being formed, a movable moldassembly to be operated by the ram of the mold press for opening andclosing the mold, said movable mold assembly including a core formingthe inside of the shot shell case, a cavity mold part encompassing thecore and defining the cavity in which the case is formed, the cavitypart cooperating with the insert part of the stationary assembly toclose the mold, said cavity part including a stripper sleeveencompassing the core in close relation to define the end of the cavityand to form the end edge of the shot shell case sidewall, the cavitypart being movable along the core when the mold is open to initiateejection of the shot shell case from the core as the stripper sleeveslides along the core, the core having a longitudinal central openingthrough which an ejector pin extends and slides, to remove the case fromthe cavity part by pushing against the inside of the base wall of thecase being formed.
 2. The invention according to claim 1 and said coreand said stripper sleeve having mating tapers engaging each other andretaining the core concentric of the cavity.